The present invention relates to a magnetic head for applying magnetic fields that vary with recorded information with respect to a heated portion in a recording region in a recording medium.
The following description will explain an example of a magnetic head used in a MiniDisk (hereinafter referred to as MD) device, while referring to FIGS. 6 through 9. FIG. 6 illustrates an arrangement of a magnetic head, while FIG. 7 is an enlarged view of a magnetic core part and a coil part of the magnetic head. FIG. 8 illustrates an arrangement of a magneto-optical recording medium, and FIG. 9 illustrates an arrangement of a magneto-optical recording-reproducing device.
First, the following description will explain an arrangement of a magnetic head while referring to FIG. 6. FIG. 6 is a cross-sectional view of a magnetic head used with a magneto-optical disk. The magnetic head includes a magnetic field generating section composed of a central magnetic pole 11 that is made of a magnetic material such as Mnxe2x80x94Zn ferrite or the like, a coil 22, and a bobbin 21 made of an insulating material, around which the coil 22 is wound in helical fashion.
This magnetic field generating section is fixed to a magnetic core holder 23 that is a contact-sliding member. Thus, a magnetic head is arranged. The magnetic core holder 23 has a sliding part 24 that is brought into contact with a magneto-optical recording medium (not shown in FIG. 6). The sliding part 24 is formed by molding with a material with a low friction coefficient which is for example a polymer material such as polyarylate, nylon, or polyester, or alternatively, ceramic. The sliding part 24 may be formed with another material, and a tape-like material with a low friction coefficient may be applied to a surface that is brought into contact with a magneto-optical recording medium.
Next, the foregoing magnetic field generating section will be described with reference to FIG. 7.
The magnetic core has an xe2x80x9cExe2x80x9d-like shape, composed of a central magnetic pole 11 and yokes 13 on the sides. The yokes 13 are positioned relatively close to the central magnetic pole 11, so as to increase the intensity of the magnetic fields.
The coil section is formed by winding the coil 22 around the bobbin 21, and by attaching it to the central magnetic pole 11 of the E-shape magnetic core. The coil 22 is a wire plated with enamel or a magnetic material (diameter: 80 xcexcm) and made of a conductive material. The bobbin 21 is aimed to make the height of the coil 22 uniform, and to prevent the coil 22 from being brought into direct contact with the central magnetic pole 11.
FIG. 8 illustrates an arrangement of a magneto-optical recording medium 40. The magneto-optical recording medium 40 is formed by providing a magneto-optical recording film 43 on a transparent substrate 41 made of polycarbonate (PC) or the like, though a dielectric film 42 made of SiN, AlN, or the like is provided between the magneto-optical recording film 43 and the transparent substrate 41. The dielectric film 42 and a reflection film 44 made of Al or the like are provided on the magneto-optical recording film 43, and on top of that, a resin protective layer 45 made of an UV curing resin is provided.
In the case of an MD, since a contact-sliding-type magnetic head is used, a lubrication film 46 made of silicon oil or the like that has a high lubricity is formed on the resin protective film 45. Incidentally, a film that constitutes a single layer implementing the functions of both the resin protective film 45 and the lubrication film 46 has been developed.
A magnetic field modulating method is explained below, with reference to FIG. 9. As shown in FIG. 9, an optical pick-up 50 for projecting laser light is provided on one side to the foregoing magneto-optical recording medium 40, while a magnetic head section 20 that is provided inside the aforementioned magnetic core holder 23 which moves according to a position of a laser spot is provided on the other side to the magneto-optical recording medium 40. The direction of the magnetic fields generated by the magnetic head section 20 is inverted in accordance with recording signals (recording information), whereby signals (information) are recorded on the magneto-optical recording medium 40.
Furthermore, to arrange the magnetic head section 20 and the magnetic core holder 23 so as to be capable of moving appropriately in spite of, if any, fluctuations of the magneto-optical recording medium 40 and dusts and projections on the same, the magnetic head section 20 and the magnetic core holder 23 are supported by a thin elastic member 31 made of metal, normally 30 xcexcm to 100 xcexcm in thickness, to which a pressure of 3 mN (milli-newton) to 10 mN is previously applied. An end of the elastic member 31 is fixed by an elastic member fixing member 32. The elastic member fixing member 32 is supported by a connecting arm 33 in a substantial xe2x80x9cLxe2x80x9d shape, so as to be connected to the aforementioned pick-up 50.
Magnetic fields generated by the magnetic head section 20 vary depending on the distance from a magnetic pole face (end surface) of the central magnetic pole 11 to the magneto-optical recording medium 40. In other words, as the distance increases, greater electric current need flow through the coil 22 in order to generate magnetic fields with a predetermined intensity to be applied to the magneto-optical recording medium 40. In the case where the distance is set constant, the intensity of the magnetic fields is proportional to the electric current. Therefore, in the case of a recording medium that for recording requires magnetic fields of a great intensity, greater electric current need be made to flow through the coil 22. This leads to a rise of the temperature in the magnetic head, that develops into serious problems such as a decrease of the intensity of the magnetic fields due to heat, and damage to the coil 22. For this reason, as the recording medium used in the magnetic field modulation recording, a recording medium requiring small recording magnetic fields has been selected, as compared with that in the case of a light intensity modulation recording medium.
Besides, also in the case where the distance between the magneto-optical recording medium 40 and the magnetic pole face of the central magnetic pole 11 greatly fluctuates, the electric current need be increased for the fluctuation, thereby leading to the same result as above. To keep constant the distance between the magneto-optical recording medium 40 and the magnetic pole face of the central magnetic pole 11, the magnetic core holder 23 for holding the magnetic field generating section composed of the central magnetic pole 11 and the coil 22 need be made of a material that allows smooth sliding, and the magnetic core holder 23 is arranged so that a level difference between the sliding part 24 and the magnetic pole face of the central magnetic pole 11 should be normally in a range of 20 xcexcm to 100 xcexcm.
By bringing the sliding part 24 into contact with the lubrication film 46 while preventing the central magnetic pole 11 from being brought into direct contact with the lubrication film 46 of the magneto-optical recording medium 40, it is made possible to keep constant the distance between the magnetic pole face of the central magnetic pole 11 and the magneto-optical recording medium 40, without a complex structure. Such a magnetic head, called as a sliding-type magnetic head, is generally used in an MD device.
Recently improvement of the recording speed and the recording density have been demanded, and to achieve it, it is required to drive the magnetic head at a higher frequency. However, when driving at a frequency exceeding several MHz, a magnetic loss of a magnetic material increases, and heat generation increases.
In a conventional magnetic head, the central magnetic pole 11 need be formed smaller and positioned as close as possible to the magneto-optical recording medium 40, in order to suppress the heat generation. As long as such a structure is applied, however, accurate position adjustment is required between a position which is irradiated by the laser from the optical pick-up 50 and the magnetic field area, which requires significant improvements in mechanical precision including transport mechanism.
An object of the present invention is to provide a magnetic head that enables improvement of the recording rate, by suppressing heat generation at the magnetic head to raise a recording frequency.
The magnetic head of the present invention is a magnetic head for switching a direction of magnetic fields applied to a temperature-rising portion in a recording region in accordance with recording information, and to achieve the foregoing object, the magnetic head is characterized by comprising (i) a single magnetic pole in a pillar shape provided on a magnetic body, having one end surface in contact with the magnetic body, and (ii) a coil that is wound around the magnetic pole so as to apply electric current for generating the magnetic fields.
According to the present invention, upon application of the magnetic fields that vary in accordance with recording information to the temperature-rising portion in the recording region, a direction of magnetization at the heated portion is changed in accordance with recording information. Thus, the recording information is recorded.
In the present magnetic head, yokes required in a conventional magnetic head having an E-shape magnetic core can be omitted, since a single magnetic pole is provided. The magnetic flux density in the magnetic pole becomes the lower for the absence of the yokes than that in the case of the conventional magnetic head that requires yokes. Since the magnetic flux density becomes lower, heat generation at the magnetic head is suppressed. In addition, since the foregoing magnetic body has a function of dissipation of heat of the magnetic pole provided on the magnetic body, the heat conducted to the magnetic body is dissipated therefrom. Thus, the cooling is conducted. Consequently, this enables further suppression of rise of temperature.
As described above, since the present magnetic head allows suppression of heat generation, the application of a greater electric current to a coil, or the recording of information at a higher frequency is enabled. Consequently, information can be recorded with magnetic fields of higher intensity.
Furthermore, since the magnetic fields can be made more intensive than that in the conventional case at the same frequency, information can be recorded with a sufficient magnetic field intensity with respect to a recording medium with an inferior sensitivity to the magnetic fields such as a magnetically induced super-resolution (MSR) recording medium. As a result, this enables the recording to a recording medium to that the conventional magnetic head cannot carry out recording.
Furthermore, according to the present invention, the absence of yokes causes the magnetic field distribution from the magnetic pole to become broad, but only a heated portion contributes to the recording, thereby allowing high-density recording to be carried out without any problems, without being affected by the magnetic field distribution.
In the foregoing magnetic head, the coil is preferably wound around in a manner such that the coil is out of contact with the magnetic pole.
In this case, even if the coating with, for example, enamel, over the coil is imperfect, contact of the coil with the magnetic pole can be surely avoided.
The foregoing coil is preferably provided on the magnetic body.
Conventionally, the coil is wound around a bobbin and encircled by yokes, thereby resulting in that heat generated at the magnetic pole and the coil is accumulated in a space defined by the bobbin and the yokes, not being dissipated to outside the magnetic head. Besides, the heat of the yokes is conducted to the coil and the magnetic pole, thereby raising the temperature at the coil and the magnetic pole. The bobbin is made of an insulating material, inferior in dissipation of heat, thereby being incapable of dissipating the heat generated by the coil. These cause the heat generated at the magnetic head to further increase.
To solve this problem, the foregoing coil is provided on the magnetic body, so that the heat generated at the coil is conducted to the magnetic body, thereby being dissipated. The heat generated at the magnetic pole is also conducted to the magnetic body, thereby being dissipated. Besides, since there are neither yoke nor bobbin that hinders dissipation of heat from the magnetic pole and heat from the coil, generation of heat at the magnetic head is surely suppressed as a whole.
Moreover, since a bobbin is unnecessary, the number of members related to the magnetic head can be reduced. Consequently, the costs and the number of steps in the process for producing the magnetic head can be surely reduced.
Furthermore, the magnetic pole preferably has a height in a range of 0.25 mm to 0.5 mm.
In this case, the rate of generation of magnetic fields can be improved, as compared with the case of the conventional magnetic head. Consequently, an improved efficiency of magnetic field generation than that in the case of the conventional magnetic head can be achieved. This leads to suppression of heat generation, thereby allowing recording at a higher frequency. This leads to an increase of a data transfer rate, thereby allowing, for example, higher image quality to be achieved in the case where images are recorded. The intensity of the recording magnetic fields can be made greater than conventionally, and therefore, the magnetic head of the present invention is applicable in the case where the magnetic field intensity required for recording is greater.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.